A new way to bag weevils

Twenty five years ago, a group led by Larry Murdock, a Purdue University professor of insect physiology, devised packaging for cowpeas, a grain grown by subsistence farmers in West and Central Africa. The packaging consists of two sealed and airtight polyethylene bags inside a woven nylon bag. The goal was to combat weevils that got into and ate the grain by cutting off their air supply and suffocating them, or at least stopping them from reproducing. Time has shown that the packaging works, but recent research proves it doesn’t work the way it was supposed to, despite saving farmers hundreds of millions of dollars over the years.

In the past, farmers sold all their cowpeas right after harvest when plentiful grain supplies pushed prices down to avoid having it eaten by weevils. Later in the year, the farmers would have to buy cowpeas for food at two to three times the price they had sold them.

After more study, Murdock recently discovered the hermetically sealed bags were actually cutting off the weevils’ ability to use oxygen in their surroundings to make water. So instead of suffocating the bugs, the bags actually made them die from thirst. This discovery could lead to a more-effective way to kill weevils: lowering the moisture content in the grain before sealing it in the bags. Researchers are also trying to see if the same packaging approach could be used with beans, corn, sorghum, and other stored grains.